Showing papers by "University of Hohenheim published in 1977"

The diminution of Heterochromatic chromosomal segments in Cyclops (Crustacea, Copepoda).

Abstract: The chromosomes of Cyclops divulsus, C. furcifer, and C. strenuus, like those of several other Copepods, undergo a striking diminution of chromatin early in embryogenesis. The process is restricted to the presumptive soma cells and occurs at the 5th cleavage in C. divulsus, at the 6th and 7th in C. furcifer, and at the 4th in C. strenus. The eliminated chromatin derives from the excision of heterochromatic chromosome segments (H-segments). Their chromosomal location is different in the three investigated species: Whereas in C. divulsus and C. furcifer the H-segments form large blocks-exclusively terminal in the former and terminal as well as kinetochoric in the latter-the germ line heterochromatin in C. strenuus is scattered all along the chromosomes. Extensive polymorphism exists with respect to the length of the terminal H-segments in C. furcifer, and with respect to the overall content of heterochromatin in the chromosomes of C. strenuus. In a local race of C. strenuus an extreme form of dimorphism has been found which is sex limited: females as a fule are heterozygous for an entire set of large (heterochromatin-rich), and a second set of small chromosomes in their germ line. Males are homozygous for the large set. In the first three cleavage divisions the H-polymorphism is solely expressed through differences of chromosome length. Following diminution the differences between homologous have disappeared. Feulgen cytophotometry demonstrates that in the three species the 1C DNA value for the germ line, as measured in sperm, is about twice that measured in somatic mitoses (germ line/soma C-values in picograms of DNA: C. strenuus 2.2/0.9, C. furcifer 2.9/1.44, C. divulsus 3.1/1.8). - The data imply that chromatin diminution is based on a mechanism which allows specific DNA segments, regardless of their location and size, to be cut out from the chromosomes without affecting the structural continuity of the remaining DNA. The mechanism may be analogous to that of prokaryotic DNA excision.

Purification and properties of pyrazon dioxygenase from pyrazon-degrading bacteria.

Abstract: Chromatography on DEAE-cellulose and gel filtration on Sephadex revealed that pyrazon dioxygenase from pyrazon-degrading bacteria consists of three different enzyme components. No component alone oxidizes the phenyl moiety of pyrazon, only when the three components are combined can oxidation be detected. Following electron paramagnetic resonance and ultraviolet measurements the protein nature of the three components was determined: component A1 (molecular weight about 180000,red-brown in colour) is an iron-sulphur protein. The existence of approximately two moles of iron and two moles of inorganic sulphur per mole of protein was demonstrated. This enzyme component was purified to homogeneity in disc electrophoresis. Component A2 is a yellow protein of a molecular weight of about 67000. FAD was shown to be the prosthetic group of this protein. Component B (molecular weight about 12000, brown in colour) is a protein of the ferredoxin type, which was purified to homogeneity, as demonstrated by disc electrophoresis. A hypothetical scheme for the cooperation of the three components is proposed: component A2 accepts as cosubstrate NADH and functions as a ferredoxin reductase. The ferredoxin, component B, has the function of an electron carrier. The conversion of the substrates is effected by component A1, the terminal dioxygenase.

Die Kristallstruktur der Tieftemperaturmodifikation von Ag8GeS6

Abstract: The low temperature form of Ag8GeS6 (synthetic argyrodite) is orthorhombic, space group Pna21, witha=15.149 (1),b=7.476 (2),c=10.589 (1), andZ=4. The crystal structure has been determined from 2-circle diffractometer data by means of direct methods and refined toR=0.081 for 3431 intensities. The structure consists of slightly distorted isolated GeS4 tetrahedra (mean Ge−S bond length 2.212 A) and two further sulphur atoms without bonds to the germanium atoms. The GeS4 tetrahedra and the S atoms are connected by the Ag atoms to form a three-dimensional framework. Three types of Ag coordination by S atoms are encountered. Three Ag positions have a strongly distorted tetrahedral environment, four Ag positions an approximately planar threefold coordination, while one Ag atom is almost linearly coordinated by two S atoms. The Ag−S distances are 2.56–2.94 A, 2.49–2.76 A, and 2.42–2.44 A, resp. All Ag atoms have at least one near Ag neighbour between 2.93 and 3.11 A.

Modelluntersuchungen zum Mechanismus der bakteriellen Eisenreduktion in Hydromorphen Böden

Abstract: Model experiments on the mechanism of bacterial iron-reduction in water-logged soils In model experiments, iron-reduction with Bacillus polymyxa (nit+) and Clostridium butyricum (nit−) was followed in relation to the development of pH, Eh and glucose fermentation. In parallel tubes, the influence of NO, (KNO,) and/or Mn02-Powder (Merck) on Fe(I1) formation and rH (calculated from pH and Eh) was measured. All tubes were incubated anaerobically (N2/C02 = 9/1) at 30°C. Both with Bacilluspolymyxa (nit+) as well as with Clostridium butyricum (nit−), the reduction-intensity rH decreased rapidly reaching entirely reducing conditions (rH = 0) within 2–3 days. In both cases iron-reduction and glucose utilization developed sigmoidal and miror symmetrically (Fig. 1) In the case of B. polymyxa (nit+) the addition of NO, and/or Mn02 suppressed iron-reduction nearly entirely. With C. butyricum, only Mn02 (but not nitrate) affected iron-reduction significantly. Nitrate remained unchanged throughout the incubation period, although completely reducing conditions (rH = 0) were obtained (Fig. 2). Apparently, nitrate, Mn02 or Fe203 are reduced directly and specifically rather than indirectly as a consequence of reducing metabolites and/or by a lowered redox potential in the environment. If nitrate, Mn02 and Fe203 are reduced chemically by reducing condition, the reduction sequence nitrate Mn(1V)-oxides Fe(II1)-oxides should occur in relation to pH and Eh (rH) and independently of the type of organism (nit+ or nit−) in question. This view is rejected by the results presented. With nit+ bacteria such as B. polymyxa, the enzyme nitrate reductase seems to act as one mechanism of iron- and manganese-reduction. However, with C. butyricum (nit−), another, so far unknown enzym system (ferrireductase?), should be made responsible for iron- and manganese-reduction.

Triadimefon: Mode of action in plants and fungi

Abstract: Triadimefon retarded the elongation of the upper internodes of shoots of tomato and cotton plants. The growth retardation was completely reversed by exogenously applied gibberellic acid (GA3). Growth of coleoptiles, primary leaves and roots of wheat and barley seedlings was reduced after seed treatment with triadimefon; application of GA3 did not completely counteract this growth retardation. Leaves of triadimefon-treated plants showed a darker green colour; leaves became lighter again when the growth retardation was reversed by GA3 application. When detached leaf sections were floated in triadimefon solutions or suspensions in the dark, senescence was delayed. The compound showed only a weak antagonistic effect on GA3-induced α-amylase synthesis in barley endosperm. Triadimefon strongly reduced the synthesis of gibberellin-like substances in Fusarium moniliforme. It inhibited the development of haustoria of Erysiphe graminis f. sp. hordei. Studies on its mode of action revealed that triadimefon blocked ergosterol biosynthesis in Ustilago avenae.

Effect of exercise on systemic blood pressure and heart rate in horses.

Abstract: Carotid loops were prepared in 3 horses several months prior to the experiments. Systemic blood pressure was recorded at rest and during exercise by insertion of a plastic cannula into the carotid artery. The pressure transducer was fixed at the neck of the animal. The blood pressure signal was transmitted by telemetry.

Interferenzeinflüsse in der Graphitrohrküvette am Beispiel der Bestimmung von Blei und Cadmium in biologischen und anderen Materialien

Abstract: Die Arbeit befast sich vor allem mit Fehlermoglichkeiten durch anorganische Depressionseffekte bei der Bestimmung von Elementen in der Graphitrohrkuvette. Ferner wird der Effekt von unspezifischen Signalbeeinflussungen durch Uberlagerung der spezifischen und unspezifischen Absorption untersucht. Wie Interferenzeffekte durch unterschiedliche Konzentrationen von Storpartnern gezeigt haben, fuhren auch Additions- oder Zumischverfahren bei den beschriebenen Storungen zu keinen brauchbaren Ergebnissen.

Ein Vergleich von Biotests mit chemisch—analytischen Methoden zum Nachweis von Atrazin, 2,4—D, DNOC und Napropamid im Boden

Abstract: Zusammenfassung: Der Abbau von Atrazin (2-Chlor-4-athylamino-6-isopropylamino-s-triazin), 2,4-D (2,4-Dichlorphenoxyessigsaure), DNOC (4,6-Dinitro-o-kresol) und Napropamid [2-(α-Naphtoxy)-NN-diathylpropionamid] im Boden wurde mit chemisch-analytischen Methoden und mit Biotests verfolgt und die Ergebnisse miteinander verglichen. Der biologische Nachweis erfolgte fur Atrazin mit Hirse (Sorghum-Sudangras-Hybride) in einem Gewachshaus-Test, fur 2,4-D und DNOC mit einem Kressewurzeltest (Lepidium sativum L.), und Napropamid wurde mit einem Haferwurzeltest (Avena sativa L.) nachgewiesen. Der instrumentelle Nachweis wurde fur Atrazin, 2,4-D und Napropamid gaschromalographisch und fur DNOC kolorimetrisch durchgefuhrt. Die fur die Herbizide typische Abbaukinetik konnte durch die Biotests nachgewiesen werden, der quantitative Nachweis war jedoch nicht befriedigend. Bei Atrazin und Napropamid wurde durch die Biotests ein schnellerer Abbau und bei 2,4-D und DNOC geringere Anfangskonzentrationen als durch die instrumentellen Methoden angezeigt. Mogliche Ursachen fur die Abweichungen werden diskutiert und aus den Ergebnissen gefolgert, dass quantitative Aussagen mit Biotests erst dann gerechtfertigt sind, wenn ihre Qualitat mit bewahrten chemisch-analytischen Methoden uberpruft worden ist. Summary: A comparison of bioassays with chemical methods of analysis for the determination of atrazine, 2,4-D, DNOC and napropamide in the soil The degradation of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), 2,4-D (2,4-dichlorophenoxyacetic acid), DNOC (4,6-dinitro-o-cresol) and napropamide (2-(α-naphthoxy)-NN-diethylpropionamide) in the soil was investigated using chemical methods of analysis and bioassays and the results were compared. For the biological determination, millet (a sorghum/Sudan grass hybrid) was used for atrazine in a glasshouse test, a cress (Lepidium sativum L.) root test for 2,4-D and DNOC. and an oat (Avena sativa L.) root test for napropamide. The instrumental determinations were carried out using gas chromatography for atrazine, 2,4-D and napropamide, and colorimetry for DNOC. The bioassays showed degradation kinetics typical for the herbicides but quantitative determination was unsatisfactory. Compared with the instrumental methods, bioassays indicated more rapid degradation in the case of atrazine and napropamide and lower initial concentrations in the case of 2,4-D and DNOC. Possible causes for these differences are discussed and from the results it is inferred that quantitative determinations with bioassays are only justifiable where their accuracy has been verified with established chemical methods. Resume: Comparaison d'essais biologiques avec des methodes d'analyse chimique pour la determination de l'atrazine, du 2,4-D, du DNOC et du napropamide dans le sol La degradation de l'atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), du 2,4-D (acide 2,4-dichlorophenoxyacetique), du DNOC (4,6-dinitro-o-cresol) et du napropamide (2-(α-naphthoxy-)-NN-diethylpropionamide) dans le sol a eteetudiee en utilisant des methodes chimiques d'analyse et des essais biologiques dont les resultats ont ete compares. Pour la determination biologique, un hybride de sorgho et de sudangrass a ete utilise pour l'atrazine dans un test en serre, un cresson (Lepidium sativum L.) dans un test racinaire pour le 2,4-D et le DNOC et une avoine (Avena sativa L.) dans un test racinaire pour le napropamide. Les determinations instrumentales ont ete faites en utilisant la chromatographie en phase gazeuse pour l'atrazine, le 2,4-D et le napropamide, et la colorimetrie pour le DNOC. Les bioessais ont revele une cynetique de degradation typique pour les herbicides, mais la determination quantitative ňa pas ete satisfaisante. Compares avec la methode instrumentale, les tests biologiques ont montre une degradation plus rapide dans le cas du 2,4-D et du DNOC. Les causes possibles de ces differences sont discutees et il est concludes resultats obtenus que les determinations quantitatives avec les essais biologiques sont justifiables suelement si leur precision a ete verifiee avec des methodes chimiques classiques.

[Degradation of antipyrin by pyrazon-degrading bacteria (author's transl)].

Abstract: Bacteria with the ability to grow on pyrazon as sole source of carbon were isolated from soil. They also are able to grow on antipyrin. Then three metabolites of antipyrin can be isolated from the culture fluid which were identified as 2,3-dimethyl-1-(cis-2,3-dihydro-2,3-dihydroxy-4,6-cyclohexadiene-1-yl)-pyrazolone (5) (I), as 2,3-dimethyl-1-(2,3-dihydroxyphenyl)-pyrazolone (5) (II) and as 2,3-dimethyl-pyrazolone (5) (III), respectively. Compound I and II were used as substrates for enzyme studies. A dioxygenase catalyzes the enzymatic conversion of antipyrin into compound I. In the presence of NAD as cosubstrate compound I is transformed into compound II by a dehydrogenase. A pure preparation of metapyrocatechase from pyrazon-degrading bacteria converts compound II into the dephenylated heterocyclic moiety of antipyrin (III) and into 2-pyrone-6-carboxylic acid. Based on the results of the enzymatic studies a pathway for the degradation of antipyrin is proposed.

Addition von 2‐Diazopropan an Allen. Asymmetrische Zerstörung von 1‐Pyrazolinen mit circular polarisiertem Licht

Abstract: Die 1,3-dipolare Cycloaddition von 2-Diazopropan an Allen liefert 1 und das Spiropyrazolin 2, deren thermische und photochemische Zersetzungsreaktionen untersucht werden. Die Bestrahlung von 2 mit circular polarisiertem Licht ergibt eine Anreicherung von optisch aktivem 2, das einen starken Cotton-Effekt im CD zeigt. Die Moglichkeit der Anwendung von circular polarisiertem Licht zur Losung mechanistischer Fragen beim Zerfall von 1-Pyrazolinen wird diskutiert. Addition of 2-Diazopropane to Allene. Asymmetric Destruction of 1-Pyrazolines with Circularly Polarized Light 1,3-Dipolar cycloaddition of 2-diazopropane to allene leads to 1 and the spiropyrazoline 2. The thermal and photochemical decomposition reactions of 1 and 2 are investigated. Irradiation of 2 with circularly polarized light produces a sample which displays optical acitivity and has a strong Cotton effect in the CD. The possibility of applying circularly polarized light for the solution of mechanistic problems in the decomposition of 1-pyrazolines is discussed.

Mesophilic and psychrophilic manganese-precipitating bacteria in manganese nodules of the Pacific Ocean.

Abstract: Mikrobiologische Untersuchungen an frischen, nicht-kontaminierten Manganknollen, Sedimentproben und bodennahem Wasser aus dem zentralen Bereich des Pazifischen Ozeans konnten das Vorkommen einer ubiquitaren, reichen Bakterienflora mit einem hohen Anteil an mesophilen-und psychrophilen Mangan(II)-fallenden Organismen nachweisen. In einigen Knollen wurden bis zu 106 mesophile und etwa 104 psychrophile (5–6 °C) Mangan(II)-fallende Bakterien festgestellt. Die mogliche Bedeutung dieser Bakterien fur die Genese von Manganknollen in der Tiefsee wird diskutiert.

Transport of abscisic acid from leaves to grains in wheat and barley plants

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